Tank 241-AY-102 Data Report

Lindberg, Michael J. ; Deutsch, William J.

Pacific Northwest National Laboratory (U.S.)

关键词: Digestion;    Leaching;    Alpha-Bearing Wastes;    Testing;    Time Dependence;   

DOI  :  10.2172/15010300
RP-ID  :  PNNL-14344
RP-ID  :  AC05-76RL01830
RP-ID  :  15010300

美国|英语

来源: UNT Digital Library

【 摘 要 】

This data report discusses the methods and philosophy used to characterize two samples of sludge and one sample of drainable liquid from tank 241-AY-102 at the Hanford Site. Archived samples of sludge and drainable liquid from tank 241-AY-102 were characterized in the laboratory in order to evaluate analytical methods for testing tank waste and determine the composition and leaching characteristics of this material. The tests included physical characterization, quantitative analysis of waste composition, and short-term water leach and acid digestion of the waste material. The water leach tests were conducted over time periods of one day, two weeks, and one month to determine if contact time had an impact on leachability. Comparisons of the results of the water leach tests with the acid digestions allow for an estimation of the water leachable percentage of an element. The average water leachability of Tc-99 was measured at 20% over the one-month time frame of the leach tests. There did not appear to be any temporal change in water leachability by comparing the results of the three sampling intervals. Approximately 24 to 48% of the total Cs-137 in the sludge is water leachable over a time period of one day to one month. There is a weak time dependence of cesium leachability with slightly more dissolved Cs-137 in the one-month test compared to the shorter tests. Very little Sr-90 is water leachable with a mean value of 0.7% {+-} 0.1% throughout the tests. This is similar to the leachabilities of Am-241, Pu-239, and Np-237, which had mean percentages of 0.4%, 1.0%, and 3.8%, respectively. The leachable percentages for these radionuclides did not vary significantly over the one month time frame. A relatively large percentage of the U-238 (51.6% to >100%) was found to be water leachable with a mean value of 73.7%. Sodium and molybdenum were also found to be relatively leachable with values of 40.4% and 42.4%, respectively. The remaining elements for which leachability could be calculated were Cr, Ag, Al, and Pb. The leachable percentages of these metals were all less than 5%. Leachability was not time dependent for any of these metals. The radioactivities of the alpha-emitting transuranic isotopes with half-lives greater than 20 years were measured to determine if the sum exceeded 100 nCi/g, which is the minimum value for classification of the material as transuranic (TRU) waste. Although there was a discrepancy between the two methods used to measure the radioactivity of these isotopes, the sum of the radioactivities for both methods exceeds 100 nCi/g by a factor of 10 or more. Based on these measurements, the sludge in tank 241-AY-102 would be classified as TRU waste.